i believe it is technically called a borrowed chord... as in it borrows from the other scale....it is notated with this symbol in the roman numeral system..... "b" if you are writing with a minor scale and you see say this in the roman numerals bV it means that it wants you to make that fifth chord with the major scale equivalent of the minor you are using...

and for this, if you are writing with a major scale and see this.... bv - it means that it wants you create the fifth chord with the minor scale equivalent....

My basic takeaway was anarchy for my chord progressions because there's probably a way to do anything I can imagine already set in the rules somewhere. I sometimes write the way the guy in the video said, start with something basic, then spend maybe half an hour moving stuff around until it's unrecognizable (when I want to do something different, at least).